The vasopressor-antinatriuretic (renin-angiotensin) and vasodepressor-natriuretic (kallikrein-kinin and prostaglandin-E2) systems of the kidney will be assessed respectively for their participation in prohypertensive and antihypertensive mechanisms involved during the course of two-kidney, one-clip Goldblatt hypertension in conscious dogs and rats. Attempts will be made to discriminate the renal and peripheral vascular effects of each system. Inhibitors of these systems will be selectively administered systemically in both animal models but also intrarenally into the contralateral kidney of dogs to determine their differential effects on blood pressure, vascular reactivity and renal excretory function. In addition, renal venous plasma of hypertensive dogs will be bioassayed for detection of non-renin pressor activity and pressor-potentiating activity.